


# 78.子集

def main(nums):
    result = []
    temp = []
    def backtrack(nums,startIndex):
        if temp not in result:
            result.append(temp[:])
        for i in range(startIndex,len(nums)):
            temp.append(nums[i])
            backtrack(nums,i+1)
            temp.pop()
    backtrack(nums,0)
    return result

if __name__ == "__main__":
    arr = input()
    nums = [int(i) for i in arr.split()]
    result = main(nums)
    print(result)